The present invention relates to a multiple spindle drilling machine for drilling a great number of connecting holes in landslide protection wide flange beams.
In landslide protection wide flange beams for use in construction of bridges, harbor construction works and underground construction works, as shown in FIGS. 1-(a) to 1-(c), square end plates 105 are welded and fixed to a wide flange beam or H-beam 102 at both the ends in the longitudinal direction, and a pair of reinforcing ribs 106 are fixed on both the top and bottom faces of a web 103 of the wide flange beam 102 so that the inner faces of the respective end plates 105 are connected to both the ends of the web 103, respectively. A pair of flanges 104 of the wide flange beam 102 have a great number of holes 107 drilled along the entire lengths thereof including parts close to both the ends thereof. These holes are arranged in zigzags in one or two upper rows and one or two lower rows and are spaced from one another at predetermined intervals. In the web 103, a plurality of holes 107 are drilled in two rows only in both the side portions in the longitudinal direction and they are spaced from one another at predetermined intervals. In general, in both the flanges 104 and the web 103, the distance between every two holes adjacent to each other in the longitudinal direction is set as 100 mm. When the landslide protection wide flange beam 101 is actually used, it is connected to other wide flange beam, a plate or the like. Accordingly, a high precision is required for this hole distance.
In order to drill holes while keeping the hole distance precise, according to the conventional method, drilling positions are marked on the flanges 104 and web 103, and then, the drilling operation is conducted manually by using a drilling machine. However, this manual drilling operation is a heavy work and the operation efficiency is extremely low. Further, since an error is allowed in a scale to be used for marking, precision positioning cannot be accomplished by such marking method and hence, positions of drilled holes become inaccurate.